This invention relates to a main beam for a ceiling panel suspension system and more paticularly to a main beam with an improved connector and thermal expansion absorbing section.
The main beams of ceiling panel suspension systems are configured for end-to-end connection. These main beams must be simple and economical to manufacture, quickly and easily connected, and must ensure longitudinal alignment. The connection must be secure against accidental uncoupling, but must also allow the beam to be uncoupled in case replacement of the beam becomes necessary.
One known means for connecting main beams in an end-to-end configuration is a tongue and strap configuration such as illustrated, for example, in the Beynon U.S. Pat. No. 3,928,950, dated Dec. 30, 1975. Such connections generally include a tongue protruding from the end of the web of the main beam, where the tongue is laterally displaced from the web and includes a detent laterally displaced from the tongue in the same direction to provide a rearward facing shoulder. Such connectors also laterally offset an area of the web immediately adjoining the tongue in the opposite direction of the tongue to form a vertical strap as well as an area of the web immediately rearward of the strap in the same direction as the tongue to form a groove, the tongue of the connecting beam being received in the groove behind the strap with the rearward facing shoulder of the detent engaging the rearward facing surface of the strap. The forward facing surfaces of the strap and the groove may be flared to guide the tongue of the connecting beam during insertion.
Other known tongue and strap connectors such as shown in the Cubbler, Jr., et al. U.S. Pat. No. 3,979,874, dated Sept. 14, 1976, further elongate the tongue and employ two straps and detents in the connection. The two detents of the tongue are displaced in the same direction as the tongue and engage the rearward facing surfaces of the strap. Such connectors generally displace the tongue and strap portions from the web the full width of the web.
Known tongue and strap connectors such as discussed above accomplish retention solely by the engagement of the detent with the rearward facing surface of the strap or the web. Use of the detent as the sole locking means requires close manufacturing tolerances and/or relatively heavy gauge material to avoid deflection or distortion of the connection. In addition, the tongue is necessarily elongated by engagement of the detent with the rear of the strap rather than the web at the front of the strap, particularly where two straps are required.
Still other tongue and strap connectors such as shown in the Jahn U.S. Pat. No. 3,496,690, dated Feb. 24, 1970, have attempted to shorten the length of the tongue and thus reduce the likelihood of damage thereto during shipment and during on-site handling by engaging the detent with the rearward facing shoulder of the web formed by lateral displacement of the strap. However, the lateral force holds the detent engaged by holding the tongue of one beam against the web of the other and resists further telescoping movement of the beam. This resistance may inhibit thermal expansion and result in buckling failure of the system in the event of fire.
While other, more positive connectors are known, they generally require multiple parts, increasing the difficulty in manufacture, and/or must be destroyed when disconnection is required.
Accordingly, it is the object of the present invention to obviate these and other problems of generally known connectors and to provide a novel main beam connector for a ceiling grid system.
Another object of the present invention is to provide a novel main beam which is easily and quickly connected to provide a positive and secure interlock, yet which allows disengagement without destruction of the connector.
Yet another object of the present invention is to provide a novel main beam connector having positive guide means to urge the beams into longitudinal alignment as they are mated.
A further object of the present invention is to provide a novel one piece connector integral with and formed from the beam to provide economy of manufacture.
In another aspect, fire rated ceiling panel suspension grid main beams commonly use a compressible section intermediate the ends thereof for confining the beam deformation due to thermal expansion of that section, thereby avoiding the twisting or buckling that would cause the grid to lose support for the ceiling panels. Such compressible sections include means for allowing each vertical portion of the beam--the web, flange and bead--to absorb longitudinal expansion without loss of alignment while maintaining support for the panels by the flange.
Generally, the means for allowing the flange to absorb longitudinal expansion consist of an interruption in the web which acts to concentrate the flange stress along three equally spaced lateral lines, so that the flange folds downwardly along the center line into a V-shape when subjected to compression. Such means are illustrated, e.g., in the Downing, Jr. U.S. Pat. No. 3,388,519, dated June 18, 1968; the Sauer U.S. Pat. No. 3,778,947, dated Dec. 18, 1973; and Sauer U.S. Pat. No. 3,965,631, dated June 29, 1976.
The structures for allowing the web and bead to absorb longitudinal expansion vary widely. One known structure (e.g., Sauer '631) for allowing the web and bead to absorb longitudinal expansion flattens the bead so that the opposing sidewalls are abutting, thus allowing the flattened bead portion and adjacent web to fold as a unit under compression.
Still other structures (e.g., Sauer '947), disclose a bead in which the top wall is interrupted, the sidewalls are flattened into abuttment and the web portion vertically aligned with the bead deformation includes a slot extending from the bead toward the flange.
Such bead and web compressible sections are designed to allow the bead and web to deform without dropping the ceiling panels. However, and as shown in the aforementioned patents, the bead of such sections often suffers substantial longitudinal misalignment as a result of compression, causing the beam to twist, and jeopardizing the support for the panels.
In addition, such sections generally require the removal of metal from the web and in some instances from the bead as well. This often presents manufacturing difficulties.
It is accordingly an object of this invention to obviate these and other problems to provide a novel fire rated main beam.
It is another object of this invention to provide a novel main beam capable of absorbing thermally induced longitudinal expansion without any substantial longitudinal misalignment.
A further of this invention is to provide a main beam in which the necessity of removing material from the web and/on bead in forming the compressible section is obviated.
A still further object of this invention is to provide a new and improved thermally compressible main beam for a ceiling panel suspension system in which the bead is notched and flattened and the web creased to control deformation in the presence of thermally induced longitudinal expansion.
These and many other objects and advantages of the present invention will be apparent to one skilled in this art from the claims and from the detailed description of the preferred embodiments when read in conjunction with the appended drawings.